The European Union and the United States have agreed to jointly tackle agriculture reform for the upcoming global trade negotiations this autumn, EU officials said on Wednesday. The two farm powerhouses hope the plan, soon to be officially presented to all members of the World Trade Organization (WTO), will add momentum to the Doha round of free trade talks due to continue next month in Mexico. "There is an agreement in principle," EU ambassador to the WTO Carlo Trojan told the Reuters news agency. Although details were still sketchy, diplomats said it covered the three key areas of agricultural trade -- domestic support, export subsidies and market access. Developing countries have long complained that rich nations’ farm subsidies, worth over $300 billion a year, prevent them competing on equal terms in international markets.